This invention relates generally to a method for making a flexible or rigid coated substrate having a high moisture vapor transmission rate (MVTR) including an extrusion coated layer of a breathable polymer adhered thereto, and a primer layer intermediate the substrate and the extrusion coated breathable polymer layer.
Polymer coated papers and water resistant sheathing materials are known to be useful in the construction industry, for preventing the infiltration of air and water to the interior of a building while allowing the outward passage therethrough of moisture vapor. Such materials may be flexible and used as building xe2x80x9cwraps,xe2x80x9d or may be rigid and used as structural or decorative panels in the exterior walls or roofs of buildings.
Typical breathable materials comprise a flexible or rigid substrate, overlaid with a polymer layer which has been mechanically or electrically perforated, embossed, or stretched to produce xe2x80x9cholesxe2x80x9d therethrough, said holes being small enough to substantially prevent the flow therethrough of air and water, but large enough to allow the passage of moisture vapor. An example of a breathable material, comprising a resin blended with inorganic fillers which is then extruded into a film and biaxially stretched or stretched in a single direction is EXXAIRE from Exxon Inc.
While monolithic breathable polymer films are known in the prior art, it is also known that such films, when applied to substrates utilizing the heat and pressure associated with conventional lamination processes, often delaminate from the supporting substrates.
It would be desirable to prepare a coated substrate having a high MVTR, wherein the resultant laminate would retain its structural integrity while preventing the flow therethrough of air and water but allowing the passage therethrough of moisture vapor.
Accordant with the present invention, there has surprisingly been discovered a process for preparing a coated substrate having a high MVTR. The process comprises the steps of:
providing a substrate;
applying onto a surface of the substrate a layer of a primer, comprising a polyamine or polyacetate; and
extrusion coating a monolithic layer of breathable polymer onto the layer of primer.
The coated substrate according to the present invention is particularly useful as a building wrap in its flexible form and a wall panel or roof underlayment in its rigid form.